In general, a public Internet Protocol (IP) address is assigned to each terminal accessing the Internet, and thus, each terminal may be identified based on the public IP address. However, not the public IP address but a private IP address assigned by a sharer is assigned to each terminal of a private network sharing one public IP address via the sharer. Accordingly, other servers or terminals outside the private network may know only the public IP address of the sharer but not the private IP address of a terminal within the private network, and thus, may not identify the terminal within the private network.
Thus, according to the related art, a method of storing, in a terminal, cookies including information for making a distinction between terminals to identify each terminal within the private network is proposed. However, cookies may be not only arbitrarily deleted by a user but also forged, and accordingly, accurate terminal identification has limits.